On Wednesday 13 October 2004 5:10 am, Brian Murphy wrote: > I have found out the problem is that the usb_parse_configuration > routine does not take account of descriptors which lie after the last > interface descriptor so the extralen parameters are set to 0 even though > there *is* extra information.
Which in that case would be tacked on to the endpoint descriptor in that last interface, as "extra" descriptor data. It's not clear to me what you mean by "not take account of"... > The ACM probe routine however looks for the extra descriptors in the > interface structure not in the configuration structure (where I think > they should be). CDC descriptors should normally go right after the control interface descriptor and before any status endpoint in that interface. As it says in the CDC spec, section 5.2 where it defines all the class-specific descriptors: "A class-specific descriptor exists only at the Interface level." And it then elaborates that the data interfaces don't have any. There is however device firmware that puts CDC descriptors in strange places. As Oliver noted, the CDC drivers have been adding workarounds so it can work better with such devices. (Also ones with bogus union descriptors...) > It seems that there is another dangerous bug in which any descriptors > not parsed by usb_parse_configuration are assumed to be sequential Huh? There are "extra" fields associated with configurations, interfaces, and endpoints. If you have firmware which for some reason doesn't put the CDC descriptors in the right place (after the control interface), there aren't many other places to search for them. I see no "danger"... > extra just points to some place in the raw configuration descriptor > instead to an allocated buffer which then contains a copy of any > non-standard descriptors. Since it's read-only to drivers, they shouldn't care if it's a copy or the original data. - Dave ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
